Continued support is requested for a regional high-resolution NMR facility for the study of biological systems housed in the Department of Chemistry, Purdue University. The Facility is designed to handle the severe problems of resolution and sensitivity encountered with biological macromolecules. The research proposals submitted by users of the Facility cover several general areas: structure and function of proteins, nucleic acids, membranes, and natural products; active sites of enzymes; modes of action of drugs; and physiological levels of metabolites in living cells and organisms. The Facility is based on two multinuclear spectrometers, 11.1 T narrow-bore and 4.7 T wide-bore. The efficiencies of these will be increased by adding computer controlled field shims and an off-line data processing station, which will be used for training and core research. The versatility of the Facility will be expanded by the addition of broad-banded probes and instrumentation for saturation transfer, laser CIDNP, and selective relaxation experiments. Although the primary function of the Facility is to provide an effective research tool to its users, part of the efforts of its staff are directed toward technological development in the areas of probe sensitivity, efficient multinuclear operation, variable temperature operation, custom probes for specialized experiments, and effective processing, storage, and presentation of spectra. The Facility is administered by an Advisory Committee consisting of the Principal Investigator, representative users, and nationally recognized experts in the field. Service time on the spectrometers is apportioned according to the scientific merit of the research as determined by the Advisory Committee.